Frozen Embryo Transfer (FET): How It Works and How It Differs From a Fresh Cycle

A frozen embryo transfer (FET) thaws an embryo that was frozen during an earlier IVF cycle and places it into the womb, so you skip the ovarian stimulation and egg collection stages entirely. Because the embryo already exists, an FET is a gentler, shorter process than a full fresh cycle. By the time I had my FET I had two embryos in the freezer from a previous round, and walking into that cycle without two weeks of injections ahead of me felt like a different world.

What a frozen embryo transfer is

A frozen embryo transfer uses an embryo created and frozen in a previous IVF cycle, rather than one made fresh in the current cycle. The egg collection, fertilisation in the lab, and embryo development have all already happened: see egg collection and embryo transfer for how those embryos were made in the first place. An FET cycle picks up the story at the end, preparing the womb to receive a thawed embryo. It sits within the wider IVF process we set out in IVF explained, as the step that lets one egg collection lead to more than one attempt.

How FET differs from a fresh transfer

The key difference is that a fresh transfer happens in the same cycle as egg collection, while an FET happens in a later cycle from a stored embryo. In a fresh cycle you go through about two weeks of stimulation injections, then egg collection under sedation (usually about 20 to 30 minutes as a day case), then transfer a few days later. An FET skips all of that: there is no stimulation and no egg collection, so the cycle is shorter, involves less medication, and is typically cheaper. One full fresh cycle runs to about four to six weeks; an FET cycle is usually nearer two to four weeks because the demanding early stages are already done.

Why embryos are frozen

Embryos are frozen because a single egg collection often produces more good-quality embryos than you would transfer at once. Clinics now usually transfer a single embryo to avoid the raised risk of multiple pregnancy, so any other suitable embryos can be frozen for the future. Freezing also helps in specific situations: when the womb lining is not ideal in the fresh cycle, when embryos are being genetically tested, or when there is a risk of ovarian hyperstimulation syndrome (OHSS) and your team prefers to let your body recover before transferring. Modern freezing uses vitrification, an ultra-rapid cooling method that avoids damaging ice crystals, and the large majority of good-quality embryos survive thawing. In the UK, the law now allows embryos to be stored for up to 55 years, with consent renewed at set intervals.

The FET process, step by step

An FET cycle has three main stages: preparing the womb lining, thawing the embryo, and the transfer itself.

First, your clinic prepares the lining of the womb so it is ready to receive the embryo. This is done in one of two ways: a natural cycle, which tracks your own ovulation with scans and times the transfer to it, or a medicated cycle, which uses hormone tablets or patches (oestrogen) and then progesterone to build and ready the lining on a controlled schedule. Your team chooses the approach based on how regular your cycles are.

Second, on the planned day the embryologist thaws the chosen embryo and checks that it has survived well. Third, the embryo is placed into the womb through a thin catheter guided by ultrasound: a quick procedure that does not need sedation, much like a smear test in how it feels. After that comes the same two-week wait before a pregnancy test that every transfer ends with. For me the practical relief of an FET, no sedation and no recovery day, was offset by exactly that wait feeling no shorter than the first time.

How well FET works

For most people, frozen and fresh transfers now have broadly comparable success rates, thanks to vitrification. Success still depends most on the age of the egg at the time it was collected, not the date of the transfer, so an embryo frozen at 34 carries that age advantage even if it is transferred a couple of years later. As with all fertility treatment, check what any quoted rate counts: per cycle started or per transfer, and pregnancy or live birth (live birth is the lower figure and the one that matters). Standardised regulator data from the HFEA is more comparable than individual clinic marketing. Because an FET avoids stimulation and egg collection, it is also usually cheaper than a fresh cycle, though storage fees may apply; our guide to how much IVF costs breaks the figures down.

If a transfer does not work, that is genuinely hard, and it is normal to grieve it; our guide to dealing with a failed cycle and specialist fertility counselling, which clinics often offer or refer for, can both help.

This is general information and support, not medical advice. For guidance on your own embryos, storage, and timing, speak to your GP or fertility specialist.